A base station apparatus of performing a handover (HO) processing when a mobile station (hereinafter referred to appropriately as “user equipment (UE: User Equipment)”) located in the own cell moves to a neighboring cell of another base station while maintaining a data communication, etc. in a mobile communication is conventionally known. When performing this HO processing, since information on the neighboring base stations (cells) is needed in advance, it is necessary that a neighboring-cell list that is a list of cell-identification information of the neighboring base stations (cells) is created in each base station apparatus (for example, refer to Non-Patent Literature 1). For example, as a neighboring-cell list referred to when a mobile station located in a cell of a base station (eNB: evolved Node B), to which a physical cell identifier (PCI: Physical Cell Identifier) of 500 is assigned, performs a handover in a mobile communication system of LTE (Long Term Evolution) system, a neighboring-cell list exemplified in Table 1 is created. In the neighboring-cell list in Table 1, a cell ID (Cell ID), identification information on a communications service provider (PLMN (Public Land Mobile Network) ID) and a location-registration area code (TAC: Tracking Area Code) are stored together with the physical cell identifier (PCI) with respect to each neighboring base station (cell).
TABLE 1PCICell IDPLMN IDTAC499XXXYYYZZZAAABBBCCCDDD. . .. . .. . .. . .
As a method of creating the foregoing neighboring-cell list, a method of searching peripheral base stations, which is called as “Sniffer”, and a method using receiving reports, which is called as “CGI Report”, “UEMR”, etc. are known. In the foregoing method of searching peripheral base stations, information on peripheral base stations (cells) is searched with a particular frequency (for example, 2.1 GHz) at a timing of activating a base station or in a predetermined cycle (for example, one hour or one week) that is set in advance, and a new peripheral base station is registered in the neighboring-cell list when the peripheral base station is searched. In the foregoing method using receiving reports, while not being restricted by a particular frequency, a base station collects information on a peripheral base station based on global identification information (CGI: Cell Global Identity), which is included in a measurement report (MR) received from a mobile station located in the own cell when performing a handover to the peripheral base station, and registers the information on peripheral base station in the neighboring-cell list. Since the information to be registered in the neighboring-cell list is collected by a plurality of methods in this way, there is a case that information on a method (information source) of acquiring information on the neighboring base station (cell) is included in the neighboring-cell list together with the information on the neighboring base station (cell). For example, as shown in Table 2, in a neighboring-cell list of a small-cell base station located neighboring with base stations A, B and B, information on an information source (Source) of acquiring cell ID information is stored together with the cell ID.
TABLE 2SourceCell IDSnifferASnifferBCGI ReportC
A base station of small cell smaller than a macro-cell in size (hereinafter referred to appropriately as “small-cell base station”) is also known. A base station of macro-cell (hereinafter referred to appropriately as “macro-cell base station”) is intentionally located. On the other had, the small-cell base station is not intentionally located, and is located, for example, at a position where a radio wave strength is weak.
A base station apparatus of the foregoing small-cell base station can perform a down link power control (DPC: Downlink Power Control) by measuring an interference level (CRS_Ec) of a downlink specific reference signal (CRS: Cell-specific Reference Signal) and a total downlink receiving power from neighboring cells by a peripheral listening function (for example, refer to Non-Patent Literature 2). In the conventional algorithm of DPC, a control target value of downlink transmission power to be used after that is determined based on measurement results of the foregoing measured instantaneous interference level and downlink receiving power.